The present invention relates to fiber-optic sensors and particularly to a serial interferometric fiber-optic sensor array for sensing changes in environmental conditions or physical phenomena.
Fiber-optic sensors have been developed for use in many sensing applications in a wide range of fields. This is due to the high sensitivity of optical fibers to various environmental conditions or physical phenomena which affect such optical fibers. For example, factors such as temperature, pressure, electromagnetic fields, and acoustical waves directly affect the light transmitting characteristics of optical fiber. These changes in the optical fiber produce a change in the phase of light signals traveling through that optical fiber. As a result, a measurement of the change in phase of light signals propagated through the optical fiber is representative of changes in those physical phenomena which have affected that fiber.
In recent developments, fiber-optic sensors have been implemented into sets or arrays so that a number of sensors can utilize light from a single source and provide environmental information on physical phenomena from various locations to a common processing location for subsequent processing. Such arrays of sensors can be used, for example, in various geophysical exploration and antisubmarine warfare applications.
A fiber-optic sensor array can be implemented in a variety of different configurations, some of which being very complex. Typically, a fiber-optic sensor can include a fiber input bus for carrying light to an array of sensors, with each sensor imparting information about the local environment to this light. This information can be collected by an output fiber bus and propagated to the common processing location, where information obtained from any selected one of the sensors can be readily identified and analyzed.
In the development of these fiber-optic sensor arrays a number of different approaches have been proposed by which information from each sensor in an array is demultiplexed, or separated, for individual identification from among all of the information arriving at the common processing location from the output fiber bus. Some of these approaches are based on conventional formats of frequency and time division multiplexing, while other approaches involve more optically complex and specialized schemes such as coherence multiplexing. As a result, present fiber-optic sensor arrays essentially include many optical fibers and optical components, which make them expensive and difficult to operate.